CVE-2026-65391: Apple Safari Buffer Overflow Vulnerability

CVE-2026-65391 Overview

CVE-2026-65391 is an out-of-bounds write vulnerability affecting Apple Safari and multiple Apple operating systems. The flaw exists in web content processing, where maliciously crafted web content can trigger memory corruption. Apple addressed the issue with improved bounds checking. Successful exploitation requires user interaction, typically by visiting a malicious webpage, and can lead to arbitrary code execution within the browser process context.

Critical Impact
Processing maliciously crafted web content may lead to memory corruption and potential arbitrary code execution across Safari, iOS, iPadOS, macOS, tvOS, visionOS, and watchOS platforms.

Affected Products

Apple Safari (versions prior to 26.6.1)
Apple iOS and iPadOS (versions prior to 26.6.1)
Apple macOS Tahoe (versions prior to 26.6.2), tvOS (prior to 27), visionOS (prior to 27), watchOS (prior to 27)

Discovery Timeline

2026-09-14 - CVE-2026-65391 published to the National Vulnerability Database
2026-09-16 - Last updated in NVD database

Technical Details for CVE-2026-65391

Vulnerability Analysis

CVE-2026-65391 is an out-of-bounds write flaw classified under [CWE-190] (Integer Overflow or Wraparound). The vulnerability resides in the web content processing pipeline used by Safari and Apple's WebKit-based rendering components. When Safari parses attacker-controlled web content, insufficient bounds checking allows a write operation to exceed the boundaries of an allocated buffer. This memory corruption condition can be leveraged to influence adjacent heap structures and pursue arbitrary code execution in the renderer.

Apple's advisory confirms the fix addresses the issue with improved bounds checking. Because the flaw impacts every Apple platform that ships WebKit, the attack surface extends beyond desktop Safari to mobile, wearable, and spatial computing devices. Exploitation requires the victim to load malicious content, which aligns with typical drive-by and watering-hole attack patterns targeting browsers.

Root Cause

The root cause is inadequate validation of size or index values during web content parsing. An arithmetic condition consistent with [CWE-190] allows a computed length or offset to bypass boundary checks, resulting in a write outside the intended memory region. This corrupts adjacent objects on the heap and creates conditions suitable for further exploitation.

Attack Vector

Exploitation occurs over the network via Safari or another WebKit-based application rendering hostile HTML, JavaScript, or media content. A user must interact with the malicious content by visiting an attacker-controlled page or opening a crafted document. No authentication is required. Successful exploitation compromises the confidentiality, integrity, and availability of the affected process.

No public proof-of-concept code has been released for this vulnerability. Refer to the Apple Support Document #148281 and related advisories for vendor technical details.

Detection Methods for CVE-2026-65391

Indicators of Compromise

Unexpected Safari or WebKit process crashes with signatures consistent with heap corruption, segmentation faults, or EXC_BAD_ACCESS exceptions
Outbound network connections from Safari or com.apple.WebKit.WebContent processes to newly registered or low-reputation domains
Creation of unexpected child processes or LaunchAgents following browser sessions on unpatched Apple devices

Detection Strategies

Monitor endpoint telemetry for WebKit content process crashes and correlate with recent browsing activity
Inspect crash reports under ~/Library/Logs/DiagnosticReports/ on macOS for repeated WebKit anomalies
Deploy network detection rules for known malicious payload delivery infrastructure and browser exploit kits targeting WebKit

Monitoring Recommendations

Track Safari and OS build versions across managed endpoints to identify hosts still running vulnerable releases
Alert on suspicious post-exploitation behavior such as unexpected shell spawns, credential access, or persistence mechanisms tied to browser processes
Correlate browser telemetry with DNS and proxy logs to identify redirects to suspected exploit-hosting domains

How to Mitigate CVE-2026-65391

Immediate Actions Required

Update Safari to version 26.6.1 and Apple operating systems to the fixed releases listed in Apple's advisories
Prioritize patch deployment for internet-facing users and executives who face elevated targeting risk
Restrict browsing to trusted domains and enable content filtering on managed networks until patches are applied

Patch Information

Apple has released fixes in Safari 26.6.1, iOS 26.6.1, iPadOS 26.6.1, macOS Tahoe 26.6.2, tvOS 27, visionOS 27, and watchOS 27. Administrators should consult the Apple Support Document #148281, Document #148282, Document #148286, Document #149036, Document #149037, and Document #149038 for platform-specific installation guidance.

Workarounds

Disable JavaScript in Safari for high-risk browsing contexts using the Safari Advanced settings
Deploy web content filtering and DNS-layer protections to block access to known malicious domains
Enforce Lockdown Mode on iOS, iPadOS, and macOS devices for users at elevated risk of targeted attacks

bash

# Verify installed Safari version on macOS
mdls -name kMDItemVersion /Applications/Safari.app

# Check macOS build version
sw_vers -productVersion

# Trigger software update check
sudo softwareupdate --list
sudo softwareupdate --install --all --restart